Question
Wed March 06, 2013 By: Meghana Anil

The reaction N2 (g)+ O2 (g) (equillibrium arrows)2 NO(g) contributes to air pollution when a fuel is burnt in air at a high temperature.At 1500k quillibruium constant K for it is 1.0x10-5 (no units given).Suppose [N2] =0.8 mol L-1 and [O2]=0.20 mol L-1 before any reaction occurs. Calculate the equillibrium concentraion of the reactants and the product after the mixture has been heated to 1500 k.

Expert Reply
Sun March 10, 2013

Let x amount has been decayed from reactant to product then:

  N2  +  O2  â†” 2NO

 T =0  0.8     0.20

 T=tequi.  0.8-x   0.2-x  2x

   Kc = 1.0 x 10-5

  Kc =  

  1.0 x 10-5 = (2x)2/ [(0.8 - x)(0.2 - x)] 

 

 If  x is very small, then

  0.8 – x ≈ 0.8

  0.2 – x ≈ 0.2

   1.0 x 10-5  = (2x)2/ [(0.8 )(0.2)]  

   16 x 10-6 = 4x2

  x= 4 x 10-6

  x = 2 x 10-3

Therefore the amount of reactant and product at equilibrium is as follows:

  N2 = 0.8 – 0.002 = 0.798

   O2 = 0.2 – 0.002 = 0.198

  NO = 2x 2 x 10-3 = 4 x 10-3

 
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